1. Field of the Invention
The invention relates to a torsional vibration damper in a gearbox housing.
2. Description of the Related Art
DE 10 2004 007 337 A1 describes a torsional vibration damper of the type which is usually mounted in a gearbox housing. A damping device is formed here by two damping units, which are axially offset from each other and which are connected to form a series connection. So that the torque present at a drive such as the crankshaft of an internal combustion engine can be transmitted to the damping device, an input part is attached to the drive. This input part has first actuating elements, each of which acts on a damping element of the first damping unit. The damping elements of the first damping unit are supported in turn against drive-side drive elements. Like the takeoff-side drive elements, each of which acts on a damping element of the second damping unit, the drive-side drive elements are a component of an intermediate part. The intermediate part formed by at least one hub disk-shaped, drive-side section, by a takeoff-side section, formed by two cover plates, and by a connecting section, which connects the two other sections of the intermediate part to each other in the axial direction. When torque is introduced to the damping elements of the second damping unit, this unit acts on the second actuating elements of a hub disk located radially on the outside, which acts as the output part and which is connected to a takeoff, which, for example, can be used to accept a clutch device.
The two damping units of the torsional vibration damper, which are axially offset from each other, are at least approximately equal radial distances away from the axis of rotation common to both damping units. These radii are comparatively small and are predetermined by the amount of radial space available, which is limited for the damping unit on the drive side by a starter-generator, which radially surrounds the damping unit. The small radial dimension of the torsional vibration damper allows optimal use to be made of the area radially inside the starter-generator unit, but the deformation volume available in the circumferential direction to both damping units is limited, which means that, even though the damping device has two damping units, there is still not much freedom of relative rotation available between the takeoff and the drive. As a result, the decoupling quality of the torsional vibration damper is limited, especially since only the first damping unit is located in a damping space partially filed with viscous medium so that it can provide velocity-proportional damping, whereas the second damping unit is of the so-called “dry” type and cannot provide damping of this type. The advantages of the compact dimensions, therefore, are outweighed by the disadvantage of the limited decoupling behavior.
U.S. Pat. No. 6,401,894 also describes a torsional vibration damper installed in a gearbox housing. This damper cooperates with a takeoff in the form of a clutch device with two clutch units. A clutch device of this type is usually referred as a “dual clutch” in professional circles. In contrast to the damping units of the previously described DE 10 2004 007 337 A1, the torsional vibration damper discussed in U.S. Pat. No. 6,401,894 is installed together with the clutch device in a torque-transmitting space, through which a fluid flows. This fluid thus not only provides a cooling function for the clutch units but also serves to act as a velocity-proportional damping medium when the torsional vibration damper is subjected to torsional vibration-induced forces. Although the radial distance of the damping unit of the torsional vibration damper discussed here from the axis of rotation is comparatively long, only the volume of this single damping unit is available for deformation. In addition, this torsional vibration damper is unsuitable in particular for small spaces, because, in addition to taking up a considerable amount of space in the radial direction, it also fails to show that any effort has been made to limit the amount of space it requires in the axial direction. More favorable in this respect is the torsional vibration damper proposed in DE 100 34 730 A1, FIG. 22. Because this damping unit is mounted on a small radius around the axis of rotation, however, it must be expected that the quality of the decoupling function of this single damping unit will be inadequate because of the small deformation volume available to its damping elements in the circumferential direction.
A clutch device operated in accordance with GB 2 145 495 also appears suitable for extremely small spaces. Here a torsional vibration damper is omitted, and the torsional vibrations are damped only by intentionally allowing the clutch to slip. Even in this arrangement, however, it is acknowledged that this approach to vibration damping should be limited to only small amounts of slippage on the order of less than 100 rpm in order to exclude the negative effects on the clutch device which might result from the generation of too much heat. It is thus possible to conclude that this type of slip control quickly reaches the limits of its functionality upon the occurrence of strong torsional vibrations.